Big renin is a larger (molecular weight 60,000 vs 40,000 for normal renin), relatively inactive renin which is present in large amounts in plasma of patients with Wilms' tumor and other kidney tumors which cause hyperreninism, with hypertension and hyperaldosteronism. Big renin may place normal renin in plasms of patients with diabetic nephropathy, resulting in hyporeninism, hypoaldosteronism, and hyperalemia. The proposed research involves further study of the origin, nature, and occurrence of big renin, including the significance of acid activation. Study will determine whether big resin is a prorenin (precursor of normal renin) or if it represents a reversible combination of renin with an inhibitor.